In situ synthesis of micro-plastics embedded sewage-sludge co-pyrolyzed biochar: Implications for the remediation of Cr and Pb availability and enzymatic activities from the contaminated soil

Careful designing of biochar (BC) employing biological and industrial waste materials has gained much attention to improve soil health via reducing the bioavailability of heavy metals (HMs) in the contaminated-soil. Herein, a forty-day pot experiment was conducted to explore the influence of micro plastic (MP) embedded sewage-sludge (SS). The effects of SS and MP dosage ratios (0e15%) on the physicochemical properties of the modified-biochars were also studied with slow-pyrolyzed (SBC-500 degrees C) and flash-pyrolyzed biochar (FSBC-70 0 degrees C). Our investigations found remarkable positive synergistic effects for the SBC-15% involving increased soil pH, CEC, high carbon contents, and alleviation in Cr and Pb leaching than control and FSBC-70 0 degrees C. Besides, SBC-15% containing high carbon functional groups can effectively mitigate the Cr and Pb availability stress by intensifying the adsorption or passivation in the amended-soil, thereby, significantly reducing the Cr and Pb EDTA-extractable contents. Chemical fractionation analyses further confirmed that SBC-15% addition was more helpful for Cr and Pb immobilization and ultimately reducing transfer-rate, bioconcentration-factor, and translocation-factor as compared to FSBC-15% and control due to its higher alkalinity, surface area/porosity, and available carbon functional groups. The maize biomass (root and shoot) increased by more than 50%, and the activities of soil enzymes such as urease, alkaline phosphatase, and glucosidase enzyme activities were also enhanced. This ecologically feasible strategy would pave an efficient way to make full use of the SS and MP for the biochar synthesis with excellent soil remediation performance. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The careful design of biochar using biological and industrial waste materials has received attention for improving soil health by reducing the bioavailability of heavy metals in contaminated soil. A study conducted a pot experiment to explore the impact of micro plastic embedded sewage sludge on the physicochemical properties of modified biochars. The addition of 15% slow-pyrolyzed biochar showed positive effects on soil pH, carbon content, and reducing leaching of chromium and lead, as well as promoting maize biomass and soil enzyme activities. This ecologically feasible strategy offers an efficient way to utilize sewage sludge and microplastics for biochar synthesis with excellent soil remediation performance.